A dental plate liner is a material for rebasing a denture, which has become unfitted for the oral mucosa of a patient through long-term use, and is used to repair the denture to a usable state again. As a curable material to be used for such material, there is widely used a radically polymerizable curable material formed of a monomer capable of being polymerized in the presence of a radical, and a radical polymerization initiator.
Such material is used by being cured through heating outside the mouth or directly cured in the mouth, and is often used by the latter technique, i.e., a so-called direct method, which involves inserting the material directly into the mouth of the patient, fitting the material to an oral mucosal surface, and then polymerizing and curing the material held in the mouth to perform the repair.
Hitherto, as such liner, there has been generally used a curable material including: a liquid material containing, as a main component, a polymerizable monomer, such as methyl methacrylate; and a powder material containing, as a main component, a (meth)acrylic acid-based polymer, such as polymethyl methacrylate, polyethyl methacrylate, or a copolymer of methyl methacrylate and ethyl methacrylate, and having added thereto a radical polymerization initiator typified by an organic peroxide or the like (for example, Patent Literatures 1 and 2).
As an advantage of such dental plate liner to be used through mixing of the powder material and the liquid material before use, there is given a unique time-dependent change in viscosity thereof. That is, in such dental plate liner, when the powder material and the liquid material are mixed, the (meth)acrylic acid-based polymer gradually dissolves in and swells with the polymerizable monomer. Accordingly, fluidity is high immediately after the mixing because the amount of the polymer component dissolving in and swelling with the polymerizable monomer component is small, but the dissolution and swelling proceed to increase the viscosity along with permeation of the monomer component into the polymer component. Then, after undergoing a dough state which allows plastic deformation, the mixture is brought into a dough state which does not allow plastic deformation. Simultaneously, such dental plate liner has the following function: the radical polymerization initiator is mixed in the liner to generate a radical, and after a lapse of a predetermined period of time from the mixing, polymerization and curing proceed.
Meanwhile, the rebase of a denture by the direct method is performed through: 1) an operation of arranging the dental plate liner on the dental plate mucosal surface; 2) an operation of inserting the dental plate liner into the mouth, followed by molding; and 3) an operation of removing and adjusting the dental plate liner. In this case, at the time of 2) the molding operation, when an attempt is made to mold the dental plate liner under a non-dough state having a low viscosity, a sufficient thickness cannot be secured. In contrast, when the viscosity is excessively increased, an accurate impression cannot be taken. In addition, when there is a risk in that the dental plate liner may become unremovable when directly cured owing to, for example, the presence of an undercut, 3) the dental plate liner is temporarily removed and adjusted before the curing in some cases. In those cases, the dental plate liner is removed from the mouth after being brought into a dough state which does not allow plastic deformation even by removal with a higher viscosity than that at the time of the molding.
The dental plate liner to be used through mixing of the powder material and the liquid material can facilitate clinical or technical work through good use of time-dependent changes in paste properties by performing: 1) the arranging operation during the high-fluidity period immediately after the mixing; 2) the molding operation under the subsequent dough state which allows plastic deformation; and 3) the adjusting operation under the dough state which does not allow plastic deformation.
However, the dental plate liner to be used through mixing of the powder material and the liquid material requires operations for measuring and mixing immediately before use, and complexity of the work poses a significant drawback in some cases.
For example, in contemporary Japan, which is undergoing a further transition from an aging society to a super-aging society, there is a tendency in the field of dentistry that the number of cases of office visit treatment reduces and the number of cases of home (visit) treatment increases. In such home treatment, the procedure involving measuring the amounts of the powder material and the liquid material immediately before use as described above has hygienic trouble due to dust of powder or the like and trouble due to air bubble incorporation during kneading or the like, and has a risk of giving an unpleasant feeling to an operator or a patient because of the odor and irritating property of the monomer due to high volatility of the monomer in the mixture.
Under such circumstances, as related art for alleviating the complexity of the measuring and mixing of the powder material and the liquid material, and the unpleasant feeling to be given to the operator or the patient, there are disclosures of a dental plate liner which uses no powder material. That is, there are proposals of: a paste-like resin material for a dental plate formed of a polymerizable monomer, a (meth)acrylate-based polymer, and a thermal polymerization catalyst and/or a photopolymerization catalyst (Patent Literature 3); a paste-like or clay-like repair material composition for a dental plate formed of a first component and a second component (Patent Literature 4); and a resin composition for a dental plate formed of a liquid A including a high molecular weight polymer of a (meth)acrylate or the like, a monomer, and a polymerization initiator, and a liquid B including a high molecular weight polymer of a (meth)acrylate or the like, and a monomer (Patent Literature 5).
Meanwhile, it has been pointed out that the related-art dental plate liner also has a hygienic problem of being extremely liable to be stained because, when used in the mouth, the dental plate liner is liable to, for example, be colored, have an odor, and absorb water over time. In order to alleviate such stain, there is also a proposal of a dental plate liner characterized by using a fluorine-containing (meth)acrylate and a polyfunctional (meth)acrylate (Patent Literature 6).